1. Field of the Invention
The present invention relates to a speaker for a mobile communication terminal. More particularly, the present invention relates to a speaker for a mobile communication terminal, in which a sound emission hole and a sound pressure adjustment hole are formed therethrough so as to enable sound pressure (ring back tone) to be simultaneously emitted to one side surface and an upper side of the terminal, and a resonance space is further formed, so that it is possible to elevate the degree of space utilization in the mobile communication terminal, to easily manufacture a mobile communication terminal which parallels the trend toward miniaturization, slimness and lightness, to improve the characteristics of low frequency sound of the sound pressure (ring back tone), and thus to improve the sound quality.
2. Description of the Related Art
In general, a mobile communication terminal comprises a buzzer for generating a ringing sound, a receiver for generating a received communication sound, and a vibration motor for causing vibration of the terminal. Since the buzzer can simply reproduce an alarm or homophony, there is a limitation in satisfying various demands of consumers.
FIGS. 1A and 1B are perspective views illustrating a conventional mobile communication terminal equipped with a speaker. As illustrated in FIG. 1A, a small speaker has been recently used instead of the buzzer. A small speaker used for a terminal comprises a sound generator 11 within a cover (folder) of the terminal equipped with a liquid crystal display (LCD) window, wherein the sound generator 11 comprises a vibration plate, a voice coil, a magnet, a top plate, and so on. An emission hole 12 for emitting a ring back tone generated by the small speaker is formed through the cover (folder) on the outer side thereof. Otherwise, as illustrated in FIG. 1B, the emission hole 12 is formed through the cover (folder) on the inside thereof, which comes in contact with a keypad, while having the same orientation as that of a receiver (not shown).
In the conventional mobile communication terminal as described above, it is difficult to select a mounting location and a mounting direction for the speaker, and a relatively large space is required in order to mount the speaker as compared with the buzzer. Therefore, it is not sufficient for the speaker to be applied to a small, slim and light mobile communication terminal. Further, since the emission hole 12 of the mobile communication terminal in FIG. 1A is formed in an outer side of the cover (folder), if it is covered by the human body, clothes, and so on, the amplitude of the emitted ring back tone is reduced. Therefore, a user may not recognize the ring back tone.
Further, since the emission hole 12 of the conventional mobile communication terminal in FIG. 1B is formed on the inner side of the cover (folder), which comes in contact with the keypad, while having the same orientation as that of the receiver, the amplitude of the emitted ring back tone may be reduced as the emission hole 12 is covered even when the cover (folder) is in a closed state, for example, the inner side surface of the cover (folder) is in contact with the keypad.
In order to solve the problems as described above, a terminal receiver unit equipped with a sound emission hole has been proposed. FIG. 2 is a sectional view schematically illustrating a conventional speaker for a mobile communication terminal, As illustrated in FIG. 2, the terminal receiver unit comprises a frame 22, an upper case 21, a top plate 27, a yoke 25, a printed circuit board (PCB) 28, a magnet 26, a vibration plate 23 and a coil 24.
The upper case 21 is coupled with the frame 22 to form a sound emission hole 20 for emitting a ring back tone of a predetermined amplitude, and accommodates the vibration plate 23, the top plate 27, the magnet 26 and the yoke 25. The vibration plate 23, the top plate 27, the magnet 26 and the yoke 25 are combined to form a speaker function unit for generating sound pressure (a ring back tone). In detail, the sound pressure (ring back tone) is generated by the vibration plate 23 of the elements constituting the speaker function unit. The PCB 28 is mounted on the outer circumference of the frame 22 to apply electric current to the coil 24, and the coil 24 generates electromagnetic force by using the applied electric current, so that the vibration plate 23 vibrates.
The terminal receiver unit having the construction as described above has the sound emission hole 20 and may be provided in a direction along wall surfaces as in the case of the existing buzzer when the terminal receiver unit is clamped in a terminal, so that it is possible to improve the degree of space utilization. Further, the conventional emission hole 12 formed on the outer surface or inner surface of the cover (folder) is disposed in the side surface of the cover (folder), so that the sound pressure (ring back tone) due to vibration of the vibration plate 23 is emitted to the side surface. Accordingly, it is possible to improve the straightness of the sound and to enhance the denseness of the sound pressure (ring back tone) and so forth.
However, in the conventional terminal receiver unit, the sound pressure (ring back tone) generated by the up and down vibration of the vibration plate 23 is reflected from the inner surface of the upper case 21, affects the vibration plate 23 during the up and down vibration, and reduces the amplitude of the vibration plate 23 during vibration. Therefore, only high frequency sound of the sound pressure (ring back tone) is generated and thus the characteristics of low frequency sound cannot be vividly realized. Consequently, the high and low frequency sounds of the sound pressure (ring back tone) emitted through the sound emission hole 20 are not harmonized and a homophony state, in which only one of the high and low frequency sounds is emitted, is caused.
Accordingly, there is a need for an apparatus and method for improving the sound quality of a speaker in a mobile terminal.